Terephthalate Compouds As Organic Electrode Materials For Rechargeable Batteries

With the rapid development of technology,the large-scale application of lithium ion batteries became a reality.Facing the limitation of lithium sources and the increasing of prices,developing new material system becomes an important topic for the secondary energy storage system.In view of the abundant resource,structure designable and nontoxic,organic materials were considered as the most promising alternative electrode sources.However,the intrinsic electric insulation and the dissolution to the organic electrolyte hinder the practical application of organic electrode.The work in this dissertation focuses on the improving of the rate performance in the organic electrode and depressing of the active material solubility toward the organic liquid electrolyte.The main contents and new findings in this thesis are listed as follows:?1?Simple method to improve the electronic conductivity of the organic electrode has been developed.Dilithium terephthalate?Li₂TP?/disodium terephthalate?Na₂TP?complexed with trace amount of graphene was prepared by a spray drying method.This approach can easily form porous microspheres consisting of the composite of graphene sheets and Li₂TP/ Na₂TP nanoparticles,which allows good connection between the nanosized active materials and the conducting additives.In addition,the porous structure can render the electrolyte penetrate into the spheres easily,and provide extra space to accommodate the volume change during repeated charge/discharge processes.Consequently,the enhanced electronic conductivity of the composite electrode with the larger surface area,result in better rate performance and more stable cycling performance.?2?We initially and rationally add Ag particles into organic calcium terephthalate?CaTP?to improve its electronic conductivity.The expected better rate performance is successfully achieved.Our work unveils that AgNO₃ is an effective and easily-available precursor for introducing electro-conductive metal into organic electrode materials to achieve better electronic conductivity.For further application,the CaTP was proposed as the anode material for sodium ion battery and potassium ion battery.As expected,the CaTP/Ag composites displayed the satisfying electrochemical performance in Na-ion half cell and K-ion half cell,respectively.?3?Silver terephthalate?Ag₂TP?was intentionally employed as the organic anode to in-situ generate the conductive metallic particles.Meanwhile,the simply synthesized Ag₂TP via the reaction between Li₂TP and AgNO3 in aqueous solution inherently exhibited nano structure.Combined with the architectural stability of the in-situ formed metal/organic nanocomposite,the Ag₂TP anode in Li-ion battery could display high and stable discharge capacities of average 149 mAh g^-1 at 1C for 500 cycles;while the Ag₂TP anode in Na-ion battery still exhibited satisfactory discharge capacities of average 133 mAh g^-1 at high current rate of 1C for 100 cycles.These results could represent the new advancement for organic electrodes of terephthalate salts.Furthermore,Ag₂TP was tested as the anode material in potassium ion battery.As expected,the Ag₂TP electrode displayed electrochemical activity in K-ion half cell.